You can actually skip the Sentinels if you have a Pharros' Lockstone and you take the No-Man's-Warf path into the Bastille. You need to find the Antiquated key and then open it's corresponding door. This is possible from the NMW path if you jump out the window of the tower with Lycia to skip a door and get the key.
Follow the path to the end, and there will be a room with one of the Pharros' mouth things. Inserting a lockstone will reveal two illusory walls, and one leads to an elevator that takes you right to Sinner's Rise, skipping both the Sentinels and the path distance between them and the Sinner's Rise.
Sorry I can't explain it more clearly, but it's near where you acquire the Bone Staff. If you do that, than defeating the Lost Sinner might be the quicker method of obtaining the Fragrant Branch of Yore.